JPH0322477B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD OF THE INVENTION The present invention relates to a zinc-nickel alloy plating bath. Conventional technology and its challenges It is well known that zinc-nickel alloy plating films have better anti-corrosion performance than galvanized films. It is being used. As a conventional zinc-nickel alloy plating method, for example, a method of electroplating using an acidic bath containing chloride has been proposed (Japanese Patent Publication No. 12343/1983).
However, when a plating film with a thickness of about 5 μm, which is required for corrosion resistance, is formed using this method, the plating film has poor flexibility and may crack due to the stress applied when attaching the plated parts. Occur. In such a case, the zinc-nickel alloy plating film may have a smaller sacrificial anticorrosion effect on the iron substrate than the galvanized film, resulting in inferior corrosion resistance than the galvanized film. on the other hand,
If the plating film is thin, cracks will not occur during installation, but sufficient corrosion resistance will not be achieved. Furthermore, during electrolysis, it is unavoidable that the current density distribution becomes non-uniform in the plated product, so that the plating film thickness becomes partially non-uniform. For example, in areas where the current density is higher, the plating layer may be thicker than necessary.
This further promotes the occurrence of cracks during installation. Furthermore, since the plating bath contains a large amount of highly corrosive chloride, the plating equipment becomes susceptible to corrosion. Means for Solving the Problems The present inventor has conducted extensive research in view of the problems of the prior art described above. As a result, when using an electrolytic plating bath in which amino acids or amino acid salts are added to a bath containing Zn ions, Ni ions, alkali hydroxide, Ni complexing agents, amino alcohol polymers, etc., the resulting zinc-nickel alloy It was discovered that the corrosion resistance and flexibility of the plating film, the uniformity of the plating film thickness, etc. were significantly improved, and the present invention was completed. That is, in the present invention, Zn ion 3 to 30 g/, Ni ion 0.2 to 20 g/, alkali hydroxide 20 to 300 g/, amino alcohol polymer 0.5 to 10 g/Ni complexing agent 1 to 20 mol per mol of Ni ion, and The present invention relates to a zinc-nickel alloy plating bath characterized by containing 0.01 to 20 g/amino acid or amino acid salt and having a pH of 11 or more. According to the electrolytic zinc-nickel alloy plating bath of the present invention, a zinc-nickel alloy plating film with excellent corrosion resistance and flexibility can be obtained. Cracks do not occur due to stress, and good corrosion resistance is maintained. Furthermore, when using the plating bath of the present invention, if the current density becomes non-uniform, for example, if the current density becomes high, the current efficiency will decrease accordingly, so that the plating film thickness will be uniform. gender is maintained. Therefore, it is also suitable for plating articles with complex shapes that have a wide current density distribution. Furthermore,
Corrosivity to plating equipment is reduced, reducing the cost required for corrosion protection of plating equipment. In the present invention, as a Zn ion source, Zn oxide,
Hydroxides, inorganic acid salts, organic acid salts, etc. can be used.
Specific examples include zinc oxide, zinc hydroxide, zinc sulfate, zinc carbonate, zinc ammonium sulfate, zinc acetate, zinc sulfamate, etc., and one or more of these can be used. The amount of Zn ion source used is as Zn ions.
The amount is preferably about 3 to 30 g/approximately. If it is less than 3g/, the current efficiency of plating decreases and it is difficult to obtain a sufficient plating film thickness, which is disadvantageous in terms of work efficiency.
If it exceeds 30g/, there will be a significant difference in current efficiency between the high current part and the low current part, making it difficult to obtain a uniform plating film thickness. As the Ni ion source, Ni hydroxide, inorganic acid salts, organic acid salts, etc. can be used. Specific examples thereof include nickel hydroxide, nickel sulfate, nickel carbonate, ammonium nickel sulfate, nickel sulfamate, nickel acetate, and nickel formate, and one or more of these can be used. The amount of Ni salt used is preferably about 0.2 to 20 g/Ni ion. 0.2
If the temperature is less than 1 g/g, the alloy ratio in the plating film will change due to slight fluctuations in the nickel concentration in the plating bath, making it difficult to obtain a plating film with an almost constant alloy ratio, making bath management difficult. become. while 20
If the amount exceeds 1 g/g, the loss of nickel, which is more expensive than zinc, will be large due to pumping out the bath, making it uneconomical. Known alkali hydroxides can be used, such as sodium hydroxide, potassium hydroxide, and the like. One or more of the above alkali hydroxides can be used. The amount of alkali hydroxide to be used may be about 20 to 300 g/approx.
If it is less than 20g/2, the conductivity of the plating bath will be poor, requiring a higher voltage than usual to obtain a given current, resulting in wasted power. On the other hand, if it exceeds 300g/, the white gloss of the plating film tends to change from gray semi-gloss to black-gray matte, which is generally referred to as alkali burn, during the transition to the next process after plating is completed, and it is not good. It becomes difficult to obtain a tanned appearance. Known complexing agents for Ni can be used.
For example, oxycarboxylic acids such as citric acid, tartaric acid, heptonic acid, gluconic acid, or their sodium or potassium salts, ethylenediamine, diethylenetriamine, triethylenetetramine,
Examples include amino compounds such as aminoethylethanolamine, 2-hydroxyethylaminopropylamine, N,N-dimethyl 1,3-diaminopropane, and 1-amino-4-methylpiperazine, and one or two of these More than one species can be used. The amount of the Ni complexing agent used may be approximately 1 to 20 moles per mole of Ni ions. If it is less than 1 mol, the solubility of nickel in the plating bath will be insufficient and the nickel concentration required for alloy plating cannot be maintained. On the other hand, if it exceeds 20 moles, the amount of nickel precipitated in the plating film will be significantly reduced, making it difficult to obtain a plating film with sufficient corrosion resistance. Known amino alcohol polymers can be used, such as copolymers of at least one amino compound and epihalohydrin or glycerol halohydrin (degree of polymerization of about 10 to 10,000).
etc. can be mentioned. Copolymerization can be carried out using known methods such as those described in Japanese Patent Publication No. 50-825, Japanese Patent Application Laid-Open No. 50-87934, Abstracts of the 50th Academic Conference of the Metal Surface Technology Association, pages 12-13 (1974), etc. According to the method, it is carried out as follows. That is, about 0.1 to 10 parts of an amino compound is dissolved in about 0.05 to 20 parts of water,
Epihalohydrin or glycerol halohydrin may be added dropwise at an appropriate temperature of about 20 to 100°C to polymerize. The ratio of the amino compound and epihalohydrin or glycerol halohydrin used during copolymerization is not particularly limited, but usually about 0.9 to 2 moles of epihalohydrin or glycerol halohydrin may be used per 1 mole of the amino compound. Examples of amino compounds include dimethylamine, N,N,N',N'-tetramethyl-1,3
-diaminopropane, N,N-dimethyl-1,3
-diaminopropane, N,N,N',N'-tetramethyl-1,4-diaminobutane, imidazole, 2-methylimidazole, 2-aminopyridine, 3-aminopyridine, 4-aminopyridine,
piperazine, 1-aminoethylpiperazine, N-
Examples include aminopropylmorpholine, N-aminoethylpiperidine, 2-aminoethanol, diethanolamine, and the like. Examples of epihalohydrin include epichlorohydrin, epibromohydrin, epiiodohydrin, etc., and examples of glycerol halohydrin include 1,2-dichloro-3-propanol, 1,3-diiodo-2 -propanol, 1,
Examples include 3-dibromo-2-propanol and 1,3-dichloro-2-propanol. One or two of the above amino alcohol polymers
More than one species can be used. The amount of amino alcohol polymer to be used may be about 0.05 to 10 g/approx.
If it is less than 0.05 g/l, the plating will be dull and rough, while if it exceeds 10 g/l, the adhesion between the material and the plating film will decrease. Known amino acids can be used, such as alanine, serine, aminobutyric acid, threonine, valine, norvaline, leucine, isoleucine, citrulline, phenylalanine, tyrosine,
diiodotyrosine, dioxyphenylalanine,
dibromtyrosine, proline, oxyproline,
Tryptophan, cysteine, cystine, neutral amino acids such as methionine, acidic amino acids such as aspartic acid, glutamic acid, arginine, lysine,
Examples include basic amino acids such as oxylysine, ornithine, canabamine, and histidine. Examples of amino acid salts include sodium salts and potassium salts of the above-mentioned exemplified amino acids. 1 of the above amino acids or amino acid salts
A species or two or more species can be used. The amount of amino acid and/or amino acid salt to be used may be about 0.01 to 20 g/approx. If the amount is less than 0.01 g, sufficient addition effects cannot be obtained and the gloss of the plating film is also insufficient. On the other hand, if it exceeds 20 g/min, there is no particular problem, but even better effects cannot be obtained and it is economically useless. In addition to the above-mentioned essential ingredients, the plating bath of the present invention includes:
Aldehydes such as aromatic aldehyde and cinnamaldehyde may be added to further improve the gloss, leveling, etc. of the plating film. The amount of the aldehyde used is not particularly limited, but is usually 0.01 to 2.
It may be about g/g. The plating bath of the present invention can be produced by adding predetermined amounts of each of the above components to water according to a conventional method.
The pH of the plating bath of the present invention thus obtained is 11 or more by containing a predetermined amount of alkali hydroxide. If it is less than 11, the zincate becomes unstable and the zinc concentration in the plating bath cannot be maintained within a predetermined range. When performing electroplating using the plating bath of the present invention, known electroplating methods can be employed.
Further, the electroplating conditions are not particularly limited and may be selected as appropriate, but usually the plating temperature is about 15 to 45°C and the average current density is ^about 0.5 to 10 A/dm2. The plating bath of the present invention can be used on virtually all materials to which zinc-nickel alloy can be applied. Specific examples include mild steel, spring steel, chrome steel,
Examples include chromium molybdenum steel, copper, 73 brass, 64 brass, and the like. Effects of the Invention According to the electrolytic zinc-nickel alloy plating bath of the present invention, a zinc-nickel alloy plating film with excellent corrosion resistance and flexibility can be obtained, so even if plating is applied to a thickness of 5 μm or more, the plated parts will remain intact. Cracks do not occur due to stress during installation, and good corrosion resistance is maintained. Furthermore, when using the plating bath of the present invention, if the current density becomes non-uniform, for example, if the current density becomes high, the current efficiency will decrease accordingly, so that the plating film thickness will be uniform. gender is maintained. Therefore, it is also suitable for plating articles with complex shapes that have a wide current density distribution. Furthermore,
Corrosivity to plating equipment is reduced, reducing the cost required for corrosion protection of plating equipment. Examples Examples and comparative examples are given below to further clarify the present invention. Example 1 ZnO 13g / NiSO ₄ 6H ₂ O 5.2g / NaOH 140g / Diethylenetriamine 3.8g / Amino alcohol polymer A 1.2 g / Tyrosine 0.72 g / Amino alcohol polymer A includes N,
A reaction polymer (average degree of polymerization of 500) of 1 mol of N,N',N'-tetramethyl-1,3-diaminopropane and 1 mol of epichlorohydrin was used. A plating bath (PH12.8) with the above composition was used on a 50 x 50 x 0.5 mm mild steel plate at a plating temperature of 30°C and a current density.
Electroplating was carried out at 1 A/dm ² , 4 A/dm ² or 10 A/dm ² for 10 minutes. The resulting dazzling film had good gloss. Thickness of plating film (μm)
Table 1 shows the nickel content (% by weight) in the plating film. Next, under the same conditions as above, a 0.5 mm thick mild steel plate was electroplated until the thickness of the plating film reached 5 μm. After applying stress to the obtained coated steel plate as follows, a corrosion resistance test (JIS-Z-
2371). That is,
The plated steel plate is bent 90 degrees and returned to the horizontal position, then reversely bent 90 degrees at the same bending position as above and returned to the horizontal position.The plated surface is then sprayed with salt water and the steel plate is The time taken for red rust to appear was investigated. The results are shown in Table 1.

[Table] Example 2 Sodium aspartate instead of tyrosine
When the same operation as in Example 1 was carried out except that 10 g/g was added, a plated film with good gloss was obtained. Table 2 shows the thickness of the plating film, the nickel content, and the red rust generation time.

[Table] Example 3 The same operation as in Example 1 was carried out except that 0.03 g of oxylysine was added instead of tyrosine, and a plated film with good gloss was obtained. Table 3 shows the thickness of the plating film, nickel content, and red rust generation time.

[Table] Example 4 When 0.03 g/anisaldehyde was further added to the plating bath of Example 1 and the same operation as in Example 1 was performed, a plating film with good specular gloss was obtained. Ta. Table 4 shows the thickness of the plating film, the nickel content, and the red rust generation time.

[Table] Example 5 ZnO 25g / NiSO ₄ 6H ₂ O 35.9g / NaOH 180g / Potassium hydrogen tartrate 26.3g / Ethylenediamine 21.9g / Amino alcohol polymer B 0.75g / Histidine 0.02g / Glycine 2.8g / Amino alcohol polymer B is 0.5 mole of 2-methylimidazole, N,N,N',N'-
1.5 of tetramethyl-1,3-diaminopropane
moles and 2 of 1,3-dichloro-2-propanol
A reaction polymer (average degree of polymerization 2300) with moles was used. Example 1 except for using the above bath (PH13.5)
When the same operation as above was carried out, a plated film with good gloss was obtained. Thickness of plating film,
The nickel content and red rust generation time are shown in Table 5.

[Table] Comparative Example 1 An electric lamp was produced in the same manner as in Example 1, except that the plating bath with the following composition and the plating temperature as described in Japanese Patent Publication No. 60-12343 was used, and the plating temperature was set at 35°C. I conducted a search. ZnCl ₂ 100g/ NiCl ₂・6H ₂ O 130g/ NH ₄ Cl 200g/ Polyoxyethylene alkyl ether
1.5g/ Benzalacetone 0.08g/ (adjusted to PH5.7 with 25% ammonium hydroxide) The resulting matte film showed good gloss at any current density, but The thickness and nickel content of the plating film varied greatly, and the corrosion resistance was also significantly inferior. The results are shown in Table 6.

[Table] Comparative Example 2 Electroplating was carried out in the same manner as in Example 1 except that tyrosine was not added. The resulting dazzling film was gray and matte at a current density of 1 A/dm ² and exhibited only very weak gloss at current densities of 4 and 10 A/dm ² , both of which had an appearance that was difficult to put to practical use.
Table 7 shows the thickness of the plating film, the nickel content, and the red rust generation time.

[Table] From Tables 1 to 7, when the plating bath of the present invention is used, a) there is little variation in the thickness and nickel content of the plating film with respect to changes in current density; and (b) it can be seen that a plated film having significantly superior corrosion resistance after stress loading can be obtained compared to conventional zinc-nickel alloy films.

Claims (1)

[Claims] 1 Zn ion 3 to 30 g/, Ni ion 0.2 to 20 g/, alkali hydroxide 20 to 300 g/, amino alcohol polymer 0.05 to 10 g/, Ni complexing agent 1 to 20 per mole of Ni ion. A zinc-nickel alloy plating bath characterized by containing 0.01 to 20 g/mole of an amino acid or an amino acid salt and having a pH of 11 or more.